Question

What is the value of $a+r+t$? Given $a\to$ absorptive power, $r\to$ reflective power, $t\to$ transmissive power.

Answer 1

We know that, radiant energy per unit area per unit time$\left(Q\right)$,
$Q_{incident}=Q_{absorbed}+Q_{reflected}$$+Q_{transmitted}$
$\Rightarrow Q_i=Q_a+Q_r+Q_t$
$\Rightarrow 1=\frac{Q_a}{Q_i}+\frac{Q_r}{Q_i}+\frac{Q_t}{Q_i}$
$a=\frac{Q_a}{Q_i}=\text{absorptive power}$
$r=\frac{Q_r}{Q_i}=\text{reflective power}$
$t=\frac{Q_t}{Q_i}=\text{transmissive power}$

$\Rightarrow a+r+t=1$